1. Field of the Invention
The present invention relates to an image reproducing apparatus for reproducing image data recorded on a hologram or a holographic stereogram by light exposure process. The present invention also relates to an image illuminating apparatus for irradiating light on the hologram or the holographic stereogram so as to reproduce image data recorded on the hologram or the holographic stereogram by light exposure process.
2. Related Art
A holographic stereogram can be fabricated in such a manner that, for example, an object image is captured sequentially from different view angles to obtain a number of captured images as source images and these captured images are sequentially recorded on a single sheet of hologram recording medium by a light exposure process as strips of element holograms or dot-like element holograms.
As shown for example in FIG. 26, a holographic stereogram containing parallax information only in a lateral direction can be fabricated in the following manner. That is, an object image 200 is captured (imaged) sequentially from different view angles in a lateral direction to obtain a plurality of captured images as source images 201a to 201e. Then, these captured source images 201a to 201e are sequentially displayed on a display unit of a holographic stereogram fabricating apparatus having a predetermined optical system. The displayed image is placed under laser light irradiation to cause interference between the object light undergoing modulation due to the image and reference rays of light. The interference fringes created by the interference are sequentially recorded on a hologram recording medium 202 as strips of element holograms. Thus, the holographic stereogram can be fabricated.
The holographic stereogram fabricated in the above manner contains image data, which is obtained by sequential image capture of the object image in the different view angles in the lateral direction and sequentially recorded in the lateral direction as strips of element holograms. Therefore, if a viewer looks at the holographic stereogram from a certain position with a single eye, a set of image data recorded as part of respective element holograms can be recognized as a two-dimensional image (hereinafter referred to as 2D image). Further, if the viewer looks at the holographic stereogram from a position different from that position with a single eye, then a set of image data recorded as another part of respective element holograms can be recognized as another 2D image. Accordingly, if the viewer looks at the holographic stereogram with both the eyes, owing to the parallax of the left and right eyes, the image recorded by the light exposure process can be recognized as a three-dimensional image (hereinafter referred to as 3D image).
Some applications utilizing the above mentioned holographic stereogram can be found in material such as “Akira Shirakura, Nobuhiko Kihara and Shigeyuki Baba, “Instant holographic portrait printing system”, Proceeding of SPIE, Vol. 3293, pp. 246-253, January 1998”, “Kihara, Shirakura, Baba, “Instant holographic portrait printing system”, 3D image conference 1998, July 1998” and so on. The above-introduced material discloses a printer system combined with an image pick-up apparatus for creating parallax image series created by picking up an object image and a printer apparatus for yielding a holographic stereogram or a hologram as a printed material such as a holographic stereogram fabricating apparatus for fabricating a holographic stereogram. The above printer system can provide a series of services from the step of image capture of the imaged object to a step of printing the resulting image.
As a matter of fact, when an image is reproduced from the hologram or the holographic stereogram, reproducing light determined by the reference light utilized upon recording the image are requested. As a source of the reproducing light, laser light may be utilized similarly to the situation of recording. However, if an image is recorded on a so-called rainbow hologram, Lippman hologram or the like, the light source need not be coherent. For example, an incoherent light source such as a halogen lamp may be utilized. Further, when an image is reproduced from a display hologram which displays the image for a viewer, for example, illuminating by parallel rays of light such as those of sunlight, illuminating of a substantial spot light source or a substantial parallel light source such as a spot light of a halogen lamp or the like may be utilized as reproducing light.
When an image is reproduced from the hologram or the holographic stereogram, it is desirable for the reproducing light irradiated from the light source to have an angle of divergence that is approximate to that of the reference light utilized upon recording the image. For this reason, when an image is reproduced from the hologram or the holographic stereogram, the type of light source for irradiating the reproducing light should be subjected to a certain limitation or the layout of the light source should also be subjected to a certain limitation in terms of an optical system.
When the reproducing light are incident upon the hologram or the holographic stereogram, a wave front of rays of an object light upon recording the image can be reproduced. When the viewer looks at the hologram of the holographic stereogram with both of his or her eyes, he or she can observe a 3D image such as of a cubic object. Moreover, the hologram or the holographic stereogram can have a series of time-sequential images recorded thereon. Therefore, it becomes possible for the hologram or the holographic stereogram to display not only a still 3D image but also a series of time-sequential images.
However, when an image is reproduced on the hologram or the holographic stereogram, in order for the viewer to be able to observe the reproduced image, the viewpoint of the viewer has to move in the parallax direction with respect to the hologram or the holographic stereogram. That is, the viewer has to move to shift his or her viewpoint for observing the reproduced image. For this reason, the reproduced image observed by the viewer on the hologram or the holographic stereogram will be determined depending on the arbitrariness of the viewer. In particular, if the hologram or the holographic stereogram contains image data which provides a reproduced image changing in accordance with the changing viewpoint of the viewer, such as when a plurality of 3D images are recorded or when a series of time-sequential images are recorded, thus there is a problem of discrepancy in the variation of the reproduced image depending on arbitrariness of the viewer.
On the other hand, when the reproduced image is reproduced on the hologram or the holographic stereogram, if the angle of incidence of the reproducing light is shifted with respect to the angle of incidence of the reference light which is determined upon recording the image, a situation is brought about which is approximated to a situation in which the viewer moves his or her viewpoint. With this situation, the viewer can view a reproduced 3D image or a series of reproduced time-sequential images.
For example, the applicant of the present application has filed a preceding application which corresponds to Japanese Patent laid-open gazette No. 2001-142382. According to Japanese Patent laid-open gazette No. 2001-142382, there is disclosed an image reproducing apparatus equipped with a light source that can shift so that a predetermined angle of incidence relative to the hologram is maintained. The disclosure of Japanese Patent laid-open gazette No. 2001-142382 contains an example of a dumper mechanism which controls a lever, a spring and an urging force of the spring, as a light source shifting mechanism. This image reproducing apparatus includes a mechanism in which even if the lever is deviated from its initial position, the lever recovers its initial status owing to the urging force of the spring. That is, the light source is moved as the lever is moved.
However, the mechanism of the image reproducing apparatus can provide only a single reciprocal motion from a status in which the light source is moved apart from its initial position to a status in which the light source again recovers its initial status. For this reason, when the viewer tries to look in a repetitive manner at the reproduced image, which is provided by the image reproducing apparatus, the viewer is requested to carry out the lever moving action in a repetitive manner, which is a cumbersome operation for the viewer. Further, since the image reproducing apparatus requires a viewer to carry out the lever moving action in a repetitive manner, the mechanism suffers from damages or wear in mechanical components forming the mechanism.